Process for preparing hydroxyalkyl acrylates and methacrylates



PROCESS FOR PREPARING HYDROXYALKY-L ACRYLATES AND -METHACRYLATES Jose'ph L. OBrieu, Elkins Park, and HenryJ. Schneider,

Hatboro, Pa., assignors to Rohm & Haas Company, Philadelphia, Pa., acorporation of Delaware No Drawing. Application February 14, 1957 SerialNo. 640,082

methacrylates can be preparedingood yield by the selective hydrolysis ofcorresponding vinyloxyalkyl acrylates and methacrylates. Vinyloxyalkylacrylates and methacrylates are prepared in accordance with the teachingof United States Patent No. 2,692,256.

A typical reaction within the scope of this invention may be representedstructurally, showing the preparation of 4-hydroxybutyl methacrylate, asfollows:

Selective hydrolysis of vinyloxyalkyl acrylates and methacrylates toproduce hydroxyalkyl acrylates and methacrylates may be accomplished byhydrolyzing the former with a solution of strong mineral acid. Sulfuric,hydrochloric, nitric and phosphoric acids are typical of the strongmineral acids which may be employed. Preferably the hydrolysis iscarried out in the presence of a conventional free-radicalpolymerization inhibitor, for example, hydroquinone,N,N"di-2-(1,4-naphthoquinonyl)- p-phenylenediamine and the like althoughit can be carried out in the absence of such an inhibitor. When thestarting material is relatively insoluble in water, a cosolvent such asdioxane may be used to bring about solution thereof during hydrolysis.

The following examples show embodiments of this invention.

EXAMPLE 1 Preparation of 4-hydroxybutyl methacrylate Twenty grams of4-vinyloxybutyl methacrylate (B. P. 6572/1 mm. n 1.4468) and 100 ml. of0.5% aqueous :sulfuric acid were stirred together for 16 hrs. at ambienttemperature. The organic layer was separated. After .saturating theaqueous layer with sodium chloride, the :solution was extracted withbenzene. The benzene extract was combined with the organic layer and thebenzene solution was washed with water, dried with anhydrous magnesiumsulfate and filtered. After addition of 0.2 g. of the polymerizationinhibit-or N,N'-di-2-(1,4-naphtho- 'quinonyl)-p-phenylenediamine, thebenzene was stripped off and the residue distilled at reduced pressure.The product which collected at 65-70/0.05 mm. amounted to 6.0 g. (35%yield) and was identified as 4-hydroxybutyl .methacrylate, 21 1.4518.

Analysis.-Saponification No., 360; hydroxyl no., 343. "Cal-dd for031314031355.

.solution was allowed to stand overnight.

2,877,264 Patented Mar. 10, 1959 2' EXAMPLE 2; Preparationof'Z-hydroxyethyI methacrylate Twenty grams of2-vinyloxyethylmethacrylate, 200 of 1% sulfuric acid and a fewcrystalsof hydroquinone were stirred at ambient temperature (about 30(3.). After one hour the mixture was homogeneous. The clear It was thensaturated with sodium chloride and extracted with five ml. portions ofether. Thev ether solution was treated with anhydrous potassiumcarbonate to remove water and traces of acid, and then filtered. Afterthe addition of 0,2 g, ofN,N-di-2-(1,4-naphthoquinonyl)-p-pheny1enediamine to the pot, the etherwas stripped off. The residue was distilled at reduced pressure,yielding a main fraction, B. P. 55-65 C./0.30.4 mm., 11 1.4489,identified as 2-hydroxyethy1 methacrylate. Wt. 12.8 g. (77% yield).

Analysis.Calcd for C H O Saponificationno, 431; hydroxyl no., 431.Found: Saponification no., 432; hydroxyl no., 418.. EXAMPLE 3Preparation of 4-hydroxybutyl methacrylate Fifty-seven grams of4'-vinyloxybutyl methacrylate, 570 g. of 1% aqueous sulfuric acid, 100ml. of dioxane and 0.1 g. of inhibitor, N,N'-di-2-(1,4-naphthoquinonyl)pphenylenediamine, were stirred and heated to 55-60?" C. for four hours.The resulting clear solution was cooled to room temperature andsaturated with sodium chloride. The small organiclayer was separated andthe aqueous layer extracted twice with ether. The ether extract wascombined with the organic layer. The ether solution was dried withanhydrous magnesium sulfate and filtered. After addition of a smallquantity of N,N-di-2-(1,4- naphthoquinonyl)-p-phenylenediamine, theether was stripped off at atmospheric pressure and the residue distilledat reduced pressure. The product which collected at 80-95 C./0.1-0.2 mm.amounted to 25 g. (51% yield) and was identified as 4-hydroxybutylmethacrylate.

Analysis.Calcd for C H O Saponification no., 355; hydroxyl no., 355.Found: Saponification no., 354; hydroxyl no., 382.

EXAMPLE 4 Preparation of S-hydroxypentyl methacrylate One-hundred andsix grams of 5-vinyloxypentyl methacrylate, 570 g. of 1% aqueoussulfuric acid, 100 ml. of dioxane and 0.1 g. ofN,N'-di-2-(1,4-naphthoquinonyl)-pphenylenediamine were stirred andheated to 5560 C. for four hours. The reaction mixture was cooled,saturated with sodium chloride and stirred for another fifteen minutes.The mixture was then extracted with several portions of ether. Thecombined ether extract was dried over anhydrous magnesium sulfate andfiltered. The ether was stripped off at partial aspirator pressure andthe residue distilled at reduced pressure, after the addition of 1.4 g.of N,N-di-2-(1,4-naphthoquinonyl)-p-phenyleuediamine. The product whichcollected at 90 C./0.03 0.04 mm. amounted to 33.3 g. (36% yield) and wasidentified as S-hydroxypentyl methacrylate.

Analysis.--Calcd for C H O Saponification no., 326; hydroxyl no., 326.Found: Saponification no., 325; hydroxyl no., 362.

EXAMPLE 5 Preparation of Z-hydroxyethyl acrylate Nine and three-tenthsg. of 2-vinyloxyethyl acrylate, ml. of 1% aqueous sulfuric acid and 0.1g. of hydroquinone were stirred at room temperature (about 30 C.). Afterone hour the mixture was homogeneous. The clear solution was allowed tostand overnight. It was then ture.

saturated with solid sodium five 50 ml. portions of ether. The combinedether extract was washed once with '50 ml. of potassium carbonatesolution and then dried'with anhydrous potassium carbonate and filtered.After theaddition of 0.05 g. of hydroquinone to the pot, the ether wasstripped off at atmospheric pressure to give 4.3 g. (57% yield) of aclear, yellow oil identified as 2-hydroxyethyl acrylate, 11

hydroxyl no., 484. Found: Saponification no., 496; hy-

droxyl no., 481.

chloride and 'extracted with Following the procedure of Example 5 using4-vinyloxybutyl acrylate and 5-vinyloxypentyl acrylate, respectively,there resulted in good yield, in the first instance, 4-hydroxybutylacrylate and, in the second, S-hydroxypentyl acrylate.

The hydroxyalkyl acrylates and methacrylates prepared selectivehydrolysis of the vinyloxy group will occur, and

thereafter separating the former from the reaction mix- 2. The processfor preparing lower hydroxyalkyl acryvinyloxyalkyl acrylates andmethacrylates which com ,lates and methacrylates from the correspondinglower;

prises selectively hydrolyzing the latter with a dilute aqueous solutionof a strong mineral acid at a temperature at which selective hydrolysisof the vinyloxy group will occur and in the presence of a free-radicalpolymerization inhibitor, and thereafter separating the former from thereaction mixture.

3.,The process for preparing-lower hydroxyalkyl acrylates andmethacrylates from the corresponding lower vinyloxyalkyl acrylates andmethacrylates which comprises selectively hydrolyzing the latter with adilute aqueous solution of a strong mineral acid in the presence ofdioxane at a temperature at which selective hydrolysis of the vinyloxygroup will occur, and thereafter separating the former from the reactionmixture.

4. The process for preparing lower hydroxyalkyl acrylates andmethacrylates from the corresponding lower vinyloxyalkyl acrylates andmethacrylates which comprises selectively hydrolyzing the latter with adilute aqueous solution of a strong mineral acid in-the presence ofdioxane at a temperature at which selective hydrolysis of the vinyloxygroup will occur and in the presence of a free-radical polymerizationinhibitor, and thereafter separating the former from the reactionmixture.

2,692,256 Bauer et al. Oct. 19, 1954 OTHER REFERENCES Blout et al.:Monomers, chapter on Vinyl Ethers by Schildknecht (1951) pp. 29-30.

Caldwell Oct. ll, 1949

1. THE PROCESS FOR PREPARING LOWER HYDROXYALKYL ACRYLATES ANDMETHACRYLATES FROM THE CORRESPONDING LOWER VINYLOXYALKYL ACRYLATES ANDMETHACRYLATES WHICH COMPRISES SELECTIVELY HYDROLYZING THE LATTER WITH ADILUTE AQUEOUS SOLUTION OF A STRONG MINERAL ACID AT A TEMPERATURE ATWHICH SELECTIVE HYDROLYSIS OF THE VINYLOXY GROUP WILL OCCUR, ANDTHEREAFTER SEPARATING THE FORMER FROM THE REACTION MIXTURE.